A vehicle controller has been utilized to calculate a roadway surface estimate. In particular, the vehicle controller determines an error value indicating a difference between a desired vehicle yaw rate and a measured vehicle yaw rate. When the error value is greater than a constant threshold value, the roadway surface estimate is determined.
A drawback associated with the foregoing vehicle controller functionality, is that the vehicle controller may not update the roadway surface estimate as regularly as desired. For example, when the vehicle controller has previously determined a roadway surface estimate that is indicative of a dry roadway, and the vehicle subsequently moves over a relatively wet roadway and begins to slide, the driver may still be able to control the vehicle sufficiently such that the error value is not greater than the constant threshold value. As a result, even though the vehicle is moving over a wet roadway, the vehicle controller may not update the roadway surface estimate. Accordingly, the roadway surface estimate may not reflect the current roadway surface condition.
Accordingly, the inventors herein have recognized a need for an improved system for determining when to update a surface estimation value indicative of a roadway condition.